Axial turbomachine rotor having blade cooling

ABSTRACT

An axial turbomachine rotor is provided. The rotor includes a rotor disk and a rotor blade ring, which includes a plurality of rotor blades, each of which include a blade root, with which the rotor blade is fixed radially outward on the rotor disk, wherein the blade root is engaged with the rotor disk at the outer edge of the rotor disk in a form-closed manner in such a way that during operation of the rotor, a gap is formed between the rotor blade and the rotor disk at a predetermined surface area of the rotor disk, in which area, a plurality of impingement cooling openings is arranged, through which a cooling medium may flow from the interior of the rotor disk into the gap whereby the rotor blade is cooled using the cooling medium by means of impingement cooling.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2010/053866, filed Mar. 25, 2010 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 09004471.0 EP filed Mar. 27, 2009. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention refers to an axial turbomachine rotor having blade cooling, especially an axial turbomachine rotor with a blade ring which is formed from a multiplicity of rotor blades which can be cooled by means of impingement cooling.

BACKGROUND OF INVENTION

A turbomachine, such as a gas turbine, has a compressor and a turbine which are coupled via a rotor. The rotor has rotor blades for the compressor and rotor blades for the turbine, wherein work is performed on an operating medium in the compressor and work is produced from the operating medium in the turbine. The operating medium is heated upstream of the turbine so that the components of the turbine are subjected to a high temperature load. The rotor is conventionally provided with disks which are lined up on a shaft and on their outer edge have in each case the rotor blades which form a blade ring. On account of high mechanical and thermal loads, the service life of the disks and of the rotor blades is limited. As a measure for extending the service life, a cooling device for cooling the rotor blades and the disks is known, with which device an increase of the brittleness, especially of the material of the disks, during operation of the gas turbine is essentially limited. Furthermore, the creep behavior of the disks and of the rotor blades lies in the non-critical region so that an extended service life (or LCF: “life cycle fatigue”) is achieved.

To this end, impingement cooling of blade platforms, which is made possible by means of a separate component which is arranged between the necks of two directly adjacent rotor blades, is known from WO 2009/008944 A2.

The production and the installation of the additional component, however, are very costly.

SUMMARY OF INVENTION

It is the object of the invention to create an axial turbomachine rotor in which rotor disk and rotor blades have a long service life.

The axial turbomachine rotor according to the invention has a rotor disk and a rotor blade ring which has a multiplicity of rotor blades which in each case have a blade root by which the rotor blade is fixed radially outwards on the rotor disk, wherein the blade root engages with the rotor disk on its outer edge in a form-fitting manner in such a way that during operation of the axial turbomachine rotor a gap is formed between the rotor blade and the rotor disk in a predetermined surface region of the rotor disk, in which gap are arranged a multiplicity of impingement-cooling openings through which a cooling medium can flow from the interior of the rotor disk into the gap, as a result of which the rotor blade, and especially its platform, can be cooled by the cooling medium by means of impingement cooling and the rotor disk can be cooled by the cooling medium by means of convective cooling.

Consequently, effective cooling of the rotor disk and of the rotor blades is achieved, as a result of which the service life of the rotor blades and of the rotor disk is long. Particularly in the case of rotor disks which for each rotor blade have a retaining recess, the steeples which are provided between the retaining recesses can be particularly efficiently cooled by means of the arrangement according to the invention of the cooling passages which open out as impingement-cooling openings. Furthermore, in the case of the turbomachine rotor according to the invention the cooling medium is used efficiently, as a result of which the axial turbomachine rotor can be operated with economy of resources.

It is preferred that for each rotor blade the rotor disk, on its outer edge, has a retaining recess in which the blade root engages by its root neck which projects radially inwards and has at least one root tooth which projects from the root neck in the circumferential direction and/or in the axial direction and has a radially outer flank and a radially inner flank, wherein the root tooth is encompassed by a root tooth recess, which is provided in the retaining recess, in such a way that during operation of the turbomachine rotor the blade root bears by the radially outer flank against the root tooth recess and the gap is formed between the radially inner flank and the root tooth recess, wherein in the surface region of the root tooth recess facing the inner flank provision is made for at least one of the impingement-cooling openings so that the blade root can be impingement-cooled on the radially inner flank by the cooling medium which flows through the impingement-cooling opening. As a result, the rotor disk is advantageously exposed to throughflow by the cooling medium, and therefore cooled, in the region of the retaining recess in which stress peaks occur during operation of the axial turbomachine rotor. Furthermore, the blade root is cooled by the impingement cooling, as a result of which heat is effectively dissipated by the cooling medium from the blade root. As a result, the effect is advantageously achieved of a temperature level being established in the rotor disk in the region of the retaining recess, and in the rotor blade, in which the service life of the rotor disk and of the rotor blades is long.

Preferably, the root teeth are arranged and formed on the root neck in such a way that the blade root has a firtree profile, wherein the root tooth recesses are formed as grooves. The root teeth and the grooves preferably extend in the axial direction of the axial turbomachine rotor. Furthermore, it is preferred that the gaps are outwardly open so that the cooling medium can flow from the gaps to outside the rotor disk. As a result, cooling medium can flow constantly through the impingement-cooling openings, as a result of which continuous cooling of the rotor disk and of the rotor blades is achieved.

The rotor blade preferably has an aerodynamically effective blade airfoil and an aerodynamically effective blade platform which is arranged radially between the blade airfoil and the blade root and by its radially inner side is arranged at a radial distance from the outer edge of the rotor disk, forming the gap, wherein in the surface region of the outer edge facing the inner side provision is made for at least one of the impingement-cooling openings so that the blade platform can be impingement-cooled on its radially inner side by the cooling medium which flows through the impingement-cooling opening. Consequently, both the blade root and the blade platform can be advantageously cooled by the cooling medium, as a result of which an effective cooling of the rotor blade is achieved. It is preferred that the impingement-cooling openings are formed in such a way that the cooling medium, which flows out of the impingement-cooling openings, impinges essentially perpendicularly upon the surface of the rotor blade. As a result, the thermal efficiency of the impingement cooling is effectively high. Preferably, the rotor disk has a multiplicity of cooling passages which open out into the gaps via the impingement-cooling openings. Also, the axial turbomachine rotor is preferably an axial turbine rotor and the cooling medium is preferably cooling air.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, a preferred embodiment of an axial turbine rotor according to the invention is explained with reference to the attached schematic drawings. In the drawings:

FIG. 1 shows a perspective view of a detail of a disk of an axial turbine rotor according to the invention, and

FIG. 2 shows a perspective view of a detail of a disk with a rotor blade of the axial turbine rotor according to the invention.

DETAILED DESCRIPTION OF INVENTION

As is evident from FIGS. 1 and 2, an axial turbine rotor 1 has a disk which is arranged rotationally symmetrically around the rotational axis of the axial turbine rotor 1. Arranged on the outer edge 13 of the disk 2 are a multiplicity of rotor blades 3 which lie next to each other over the circumference of the disk 2, wherein the rotor blades 3 faun a rotor blade ring. Each rotor blade 3 has a blade airfoil 4 by which the rotor blade 3 interacts with an operating medium of the axial turbine rotor 1. The blade airfoil 4 is arranged on the disk 2 in a radially outwards extending manner, wherein the rotor blade 3, on the radially inner end of the blade airfoil 4, has a blade root 5 by which the blade airfoil 4 is fastened on the disk 2. Between the blade airfoil 4 and the blade root 5, a blade platform 6 is formed on the rotor blade 3 and extends in the axial direction and in the circumferential direction of the axial turbine rotor 1, wherein the radially outer side of the blade platform 6 is arranged facing the operating medium and the radially inner side 18 of the blade platform 6 is arranged facing the disk 2.

The blade root 5 has a root neck 7 which extends radially inwards from the blade platform 6. A multiplicity of root teeth 8 are foamed on the root neck 7, pointing in the circumferential direction of the axial turbomachine rotor 1, wherein the root teeth 8 are arranged symmetrically to the longitudinal axis of the root neck 7. A retaining recess 9 is formed for each blade root 5 on the outer periphery of the disk 2 and has grooves 10 in which engage the root teeth 8. The retaining recess 9 with its grooves 10 is patterned on the contour of the blade root 5 with the root teeth 8 so that the blade root 5 engages in a form-fitting manner with the retaining recess 9. Owing to the fact that each root tooth 8 engages in the groove 10 assigned to it and is encompassed by the material of the disk 2, the blade root 5 is fixed in the retaining recess 9 in the radial direction. The outer region of the rotor disk 2 between two directly adjacent retaining recesses 9 is also referred to as a steeple in this case.

The root teeth 8 are arranged on the root neck 7 essentially in a manner in which they extend in the axial direction of the axial turbine rotor 1 so that in the same way the grooves 10 also have an extent in the axial direction of the axial turbine rotor 1. Furthermore, the root teeth 8 are arranged parallel to each other and consequently the grooves 10 are also arranged parallel to each other so that the rotor blade 3, for mounting on the disk 2 or for removing from the disk 2, can be inserted in the retaining recess 9 or withdrawn from the retaining recess 9 by its blade root 5 in the axial direction. Furthermore, the root teeth 8 are designed with a round contour and the grooves 10 are similarly designed with a corresponding round contour so that on account of notch stress effects the stress level in the disk 2 and in the blade root 5 is low during operation of the axial turbine rotor 1.

Each root tooth 8 has a radially inner flank 16 and a radially outer flank 17, wherein the flanks 16, 17 are formed in an inclined manner to each other. In particular, the radially outer flank 17 is inclined to the circumferential direction of the disk 2 in such a way that the radius of the radially outer flank 17 reduces away from the root neck 7. During operation of the axial turbine rotor 1, a centrifugal force, which acts radially outwards, acts upon the rotor blade 3. On account of the inclination of the radially outer flank 17 and the corresponding contouring of the groove 10, a self-centering effect of the blade root 5 in the retaining recess 9 is created. In this case, the radially outer flank 17 bears against the groove 10 so that the root tooth 8 is supported in the groove 10 radially towards the outside on the radially outer flank 17. The groove 10 is formed around the root tooth 8 with clearance so that an undesirable seizing of the blade root 5 in the retaining recess 9 is prevented, as a result of which the self-centering effect by means of the root teeth 8 and the grooves 10 is undisturbed. Owing to the fact that during operation of the axial turbine rotor 1 the root tooth 8 is in touching contact by its radially outer flank 17 with the groove 10, a gap 11 ensues on account of the clearance on the radially inner flank 16. In the region of the groove 10 which is freed as a result of the gap 11, provision is made for a multiplicity of impingement-cooling openings 12 through which cooling air flows. If the cooling air discharges from the impingement-cooling openings 12, the cooling air flows into the gap 11 and cools the root tooth 8 on the radially inner flank 16 by means of impingement cooling. The retaining recess 9 is formed on the disk 2, being open on the end face side, so that as a result of the gaps 11 on the radially inner flanks 16, outwardly open cooling passages are formed. The cooling air enters the cooling passages through the impingement-cooling openings 12 and flows through the cooling passages and discharges on the end face side on the disk 2.

The blade platform 6 is arranged at a radial distance on the outer edge 13 of the disk 2 so that a gap 14 is formed between the outer edge 13 of the disk and the radially inner side 18 of the blade platform 6, beneath the radially inner side 18. A multiplicity of impingement-cooling openings 15, through which cooling air flows, are formed in the region of the gap 14 in the outer edge 13 of the disk. The cooling air impinges upon the radially inner side 18 so that the blade platform 6 is cooled by the cooling air by means of impingement cooling. As a result of the gap 14, a cooling passage is fanned on the outer edge 13 of the disk and is outwardly open around the blade platform 6. As a result, the cooling air from the impingement-cooling openings 15 on the outer edge 13 of the disk can discharge to the outside past the blade platform 6. During operation of the axial turbine rotor 1, the radially outer side of the blade platform 6 is in contact with hot gas, as a result of which there is a high heat yield to the blade platform 6 during operation of the axial turbine rotor 1. The heat which is transferred to the cooling air on the radially inner side 18 of the blade platform 6 is transported away from the blade platform 6 by means of convection. 

1.-9. (canceled)
 10. An axial turbomachine having a rotor disk and a rotor blade ring, comprising: a plurality of rotor blades, each including a blade root by which the rotor blade is fixed radially outwards on the rotor disk; and a plurality of impingement-cooling openings, wherein the blade root engages with the rotor disk on an outer edge of the rotor disk in a form-fitting manner in such a way that during operation of the axial turbomachine rotor, a gap is formed between the rotor blade and the rotor disk in a predetermined surface region of the rotor disk, and wherein in the gap are arranged the plurality of impingement-cooling openings through which a cooling medium may flow from an interior of the rotor disk into the gap, as a result of which the rotor blade is cooled by the cooling medium by means of impingement cooling and the rotor disk is cooled by the cooling medium by means of convective cooling.
 11. The axial turbomachine rotor as claimed in claim 10, wherein the rotor disk, on its outer edge, includes a retaining recess, in which the blade root engages by its root neck which projects radially inwards and includes a root tooth which projects from the root neck in a circumferential direction and/or in the axial direction and includes a radially outer flank and a radially inner flank, wherein the root tooth is encompassed by a root tooth recess which is provided in the retaining recess in such a way that during operation of the turbomachine rotor the blade root bears by the radially outer flank against the root tooth recess and a first gap is formed between the radially inner flank and the root tooth recess, and wherein in a surface region of the root tooth recess facing the inner flank provision is made for a first impingement-cooling opening so that the blade root may be impingement-cooled on the radially inner flank by the cooling medium which flows through the first impingement-cooling opening.
 12. The axial turbomachine rotor as claimed in claim 11, wherein the root tooth is arranged and formed on the root neck in such a way that the blade root includes a firtree profile, and wherein the root tooth recess is formed as a groove.
 13. The axial turbomachine rotor as claimed in claim 12, wherein the root tooth and the groove extend in the axial direction.
 14. The axial turbomachine rotor as claimed in claim 10, wherein the gap is outwardly open so that the cooling medium may flow from the gap to outside the rotor disk.
 15. The axial turbomachine rotor as claimed in claim 10, wherein the rotor blade includes an aerodynamically effective blade airfoil and an aerodynamically effective blade platform which is arranged radially between the blade airfoil and the blade root and by its radially inner side is arranged at a radial distance from the outer edge of the rotor disk, forming a second gap, and wherein in a surface region of the outer edge facing an inner side provision is made for a second impingement-cooling opening so that the blade platform may be impingement-cooled on its radially inner side by the cooling medium which flows through the second impingement-cooling opening.
 16. The axial turbomachine rotor as claimed in claim 10, wherein the plurality of impingement-cooling openings are formed in such a way that the cooling medium, which flows out of the impingement-cooling openings, impinges essentially perpendicularly upon a surface of the rotor blade.
 17. The axial turbomachine rotor as claimed in claim 15, wherein the rotor disk includes a plurality of cooling passages which open out into the second gap via the second impingement-cooling opening.
 18. The axial turbomachine rotor as claimed in claim 10, wherein the rotor disk includes a plurality of cooling passages which open out into the gap via the plurality of impingement-cooling openings.
 19. The axial turbomachine rotor as claimed in claim 10, wherein the axial turbomachine rotor is an axial turbine rotor and the cooling medium is cooling air.
 20. The axial turbomachine rotor as claimed in claim 15, wherein the axial turbomachine rotor is an axial turbine rotor and the cooling medium is cooling air. 